- Jordan Evans, Texas A&M University, College Station
Inconel 600, 316L stainless steel, and oxide dispersion strengthened steel rods were fabricated in three orientations (vertical, 45°, horizontal) using laser additive manufacturing (LAM), and conventionally manufactured rods were purchased from a commercial vendor as controls. All rods were similarly heat treated with no cold working. Alloys were characterized in their unirradiated as-annealed states using a variety of techniques such as XRD, SEM/EDS, TEM/STEM, SPM, EBSD, nanoindentation, and bulk tensile testing. The samples were irradiated using neutrons (low dose) and self-ions (high dose), then were characterized again to investigate the LAM build orientation dependence of the mechanical and microstructural changes induced by radiation damage. In general, rods built by LAM had anisotropic unirradiated microstructural, textural, and mechanical properties. Additionally, LAM rods showed a variety of anisotropic changes due to radiation damage. Build direction-dependent empirical relationships are provided that approximately fit the radiation-induced hardening and segregation data. A relationship that closely fits the measured data was also derived based on thermal diffusion theory and crystallographic geometry principles. Finally, a method was proposed based on melt pool solidification thermodynamics that utilizes a heated powder bed stage to potentially reduce the residual strain, microstructural anisotropy, and grain boundary disorder of specimens built by LAM.